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authorDaniel Axtens <dja@axtens.net>2015-05-12 13:23:59 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2015-05-12 19:44:01 +1000
commitffb2d78eca08a1451137583d4e435aecfd6af809 (patch)
tree223ad3754bf3073f65509dfc045cb70290c429a2 /arch/powerpc/kernel/mce.c
parent7b868e81be38d5ad4f4aa4be819a5fa543cc5ee8 (diff)
powerpc/mce: fix off by one errors in mce event handling
Before 69111bac42f5 ("powerpc: Replace __get_cpu_var uses"), in save_mce_event, index got the value of mce_nest_count, and mce_nest_count was incremented *after* index was set. However, that patch changed the behaviour so that mce_nest count was incremented *before* setting index. This causes an off-by-one error, as get_mce_event sets index as mce_nest_count - 1 before reading mce_event. Thus get_mce_event reads bogus data, causing warnings like "Machine Check Exception, Unknown event version 0 !" and breaking MCEs handling. Restore the old behaviour and unbreak MCE handling by subtracting one from the newly incremented value. The same broken change occured in machine_check_queue_event (which set a queue read by machine_check_process_queued_event). Fix that too, unbreaking printing of MCE information. Fixes: 69111bac42f5 ("powerpc: Replace __get_cpu_var uses") CC: stable@vger.kernel.org CC: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> CC: Christoph Lameter <cl@linux.com> Signed-off-by: Daniel Axtens <dja@axtens.net> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel/mce.c')
-rw-r--r--arch/powerpc/kernel/mce.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index 15c99b649b04..b2eb4686bd8f 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -73,7 +73,7 @@ void save_mce_event(struct pt_regs *regs, long handled,
uint64_t nip, uint64_t addr)
{
uint64_t srr1;
- int index = __this_cpu_inc_return(mce_nest_count);
+ int index = __this_cpu_inc_return(mce_nest_count) - 1;
struct machine_check_event *mce = this_cpu_ptr(&mce_event[index]);
/*
@@ -184,7 +184,7 @@ void machine_check_queue_event(void)
if (!get_mce_event(&evt, MCE_EVENT_RELEASE))
return;
- index = __this_cpu_inc_return(mce_queue_count);
+ index = __this_cpu_inc_return(mce_queue_count) - 1;
/* If queue is full, just return for now. */
if (index >= MAX_MC_EVT) {
__this_cpu_dec(mce_queue_count);